Means and method of cleaning information-carrying tape

ABSTRACT

A means and method for cleaning elongated axially extending information-carrying tape is provided. The tape is passed over a plurality of slots positioned transversely to the longitudinal axis of the tape with each of the slots defining a cleaning edge and having a vacuum chamber thereunder. A pulsating vacuum is applied to the vacuum chamber to cause portions of the tape to be moved toward the vacuum chamber during passage over the slots with all portions of the tape being cleaned by vacuum action and by a scraping of the cleaning edge. The tape cleaning means has a plurality of seriatim arranged slots defined in part by seriatim arranged scraping edges. Means for passing the tape over the slots is provided and a vacuum chamber underlies the slots. A means for applying a pulsating vacuum to the chamber is provided so that portions of the tape are urged into the slots as the tape is moved thereover whereby unwanted material is removed from the tape by the vacuum and by the scraping action of the scraping edges.

nited States Patent [72] Inventor Pierre G. Foret Sudbury, Mass. [21] Appl. No. 824,061 [22] Filed May 13, 1969 [45] Patented Nov. 16,1971 {73] Assignee P. G. Foret Inc. Sudbury, Mass.

[54] MEANS AND METHOD OF CLEANING INFORMATION-CARRYING TAPE 16 Claims, 5 Drawing Figs.

[52] US. Cl 134/9, 15/93, 15/308,15/404,134/15,134/21 [51] Int. Cl B08b 5/04, B08b 7/02 [50] Field of Search 134/6, 9, 15, 21; 15/93, 100, 306, 308, 404

[56] References Cited UNITED STATES PATENTS 1,561,321 11/1925 Goodman 15/404 1,839,793 l/l932 Lewis 15/404 2,257,574 9/1941 Ray 15/404 3,091,794 6/1963 Pillsbury 15/308 1 11,2/!2 9y11 5m m Ht 39 Primary Examiner-Joseph Scovronek Assistant Examiner-Joseph T. Zatarga Attorney-Wolf, Greenfield & Sacks ABSTRACT: A means and method for cleaning elongated axially extending information-carrying tape is provided. The tape is passed over a plurality of slots positioned transversely to the longitudinal axis of the tape with each of the slots defining a cleaning edge and having a vacuum chamber thereunder. A pulsating vacuum is applied to the vacuum chamber to cause portions of the tape to be moved toward the vacuum chamber during passage over the slots with all portions of the tape being cleaned by vacuum action and by a scraping of the cleaning edge. The tape cleaning means has a plurality of seriatim arranged slots defined in part by seriatim arranged scraping edges. Means for passing the tape over the slots is provided and a vacuum chamber underlies the slots. A means for applying a pulsating vacuum to the chamber is provided so that portions of the tape are urged into the slots as the tape is moved thereover whereby unwanted material is removed from the tape by the vacuum and by the scraping action of the scraping edges.

MEANS AND METHOD OF CLEANING INFORMATION- CARRYING TAPE BACKGROUND OF THE INVENTION The cleaning of various information-carrying tapes such as computer tapes, video tapes, audio tapes and the like has become an increasing problem in the art as the magnetic tape art has advanced. Computer tapes formed of a Mylar backer with an oxide coating containing magnetizable particles have been developed from a stage where 200 bits per inch were formerly employed and now use of from 1,600 to 3,200 bits per inch is known. As the number of bits per inch in such tapes increase, cleaning becomes more critical. Atmospheric dust, loose oxide particles and other contaminates on the tape surface can create transmission error of the tape in conventional recording and reproducing apparatus.

Surface defects on or partially embedded in the oxide coatings of the tape can be caused by improper coating techniques or can be developed through normal wear and tear of the tapes. Such surface defects include raised oxide particles, polyester fibers or airborne dust particles which become partially or completely lodged in the coated surface with resulting data errors due to resultant tape to recording head separation. The defects may be of the loose type such as dust particles merely lying on the surface or of the transient type where dust, oxide or other particles, which may have been originally lying on the surface, become permanently em bedded over a period of time when the tapes are wound on reels.

The prior art has attempted to remove surface defects by a variety of different means and methods including razorlike blades passing over the tape to shave the surface, rotary blade and disc devices or other scraping devices to remove oxide particles and dust. The known means and methods for cleaning tape sometimes result in unwanted tape wear or damage to tape surfaces and edges. In some cases, the tapes are cut or creased and/or a considerable number of surface defects are not removed. Often frequent changing of scraping heads is necessary and it is difficult to rapidly tell when a scraping head has worn down making adjustment and alignment difficult. Costs of cleaning are often high and inordinately long times sometimes necessary.

It is an object of the present invention to provide a means and method for the rapid and efficient cleaning of informationcarrying tape.

Another object of this invention is to provide a means and method in accordance with the above object which provides excellent tape cleaning with simplified apparatus and minimized damage during cleaning.

SUMMARY OF THE INVENTION According to the invention an information-carrying tape cleaning device has a means defining a plurality of seriatim arranged slots defined in part by seriatim arranged scraping edges. Means are provided for passing the tape over the slots with a vacuum chamber underlying the slots. Means are provided for applying a pulsating vacuum to the chamber as the tape is moved over the slots to urge portions of the tape into the slots as the tape is moving whereby unwanted material is removed from the tape by the vacuum and by the scraping action of the scraping edges. The slot dimensions, pulsating vacuum and tape speed are predetermined to provide a cleaning action over the entire surface of the tape facing the slots as it is continuously passed over the series of slots from one end to the other.

Preferably the slots are formed in a cleaning head having an underlying vacuum chamber interconnected with an electropneumatic high-frequency valve which is in turn connected to a vacuum pump or source of constant vacuum and a pulsating power supply.

According to the method of this invention an elongated tape is cleaned on one surface by subjecting at least two spaced portions of the tape surface to a pulsating vacuum cleaning action while axially moving the tape. Preferably an elongated axially extending information-carrying tape is cleaned on one surface by passing the tape over a plurality of slots positioned transverse to the longitudinal axis of the tape with each of the slots preferably being defined in part by a scraping edge and having a vacuum chamber thereunder. A pulsating vacuum is applied to the vacuum chamber to cause portions of the tape to be moved toward the vacuum chamber during passage over the slots with those portions being cleaned by vacuum action and preferably by a scraping action of the scraping edges without damaging the tape. The vacuum is pulsed at a predetermined preferably constant rate coordinated with the rate of movement of the tape over the slots and the size and number of slots so that each portion of the tape passing over the slots is urged into at least one of the slots during a single passage of the tape thereover.

The method is a dry cleaning method and acts to shake the tape much in the manner of shaking a rug to remove loose particles. Preferably the tape is unreeled from a substantially freewheeling reel and back tension on the tape is provided by the vacuum action so that the winding tension can be predetermined to a constant value.

It is a feature of this invention that the tension on the tape can be adjusted as desired by predetermination of the vacuum conditions so that a drive reel pulling the tape over the vacuum source can have variable speed but constant drag. This feature prevents unwanted stresses and stretching of the tape during cleaning which if uncontrolled could damage the tape.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be better understood from a reading of the following specification with reference to the drawings in which:

FIG. 1 is a semidiagrammatic side view of a preferred em bodiment of a tape cleaning device in accordance with the present invention with portions shown in cross section;

FIG. 2 is a top plan view of an element thereof;

FIG. 3 is a diagrammatic cross-sectional side view of an element thereof illustrating the cleaning action of the device; and,

FIGS. 4 and 5 are diagrammatic illustrations of the degree of cleaning at two tape velocity extremes in a tape cleaning device in accordance with the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS With reference now to the drawings and more particularly FIGS. 1-3, a computer tape cleaning device is generally illustrated at 10 and comprises a cleaning head 11, an electropneumatic valve 12, a vacuum pump l3 and a pulsating electric power supply 14.

The cleaning head 11 is a generally rectangular enclosed box having upstanding side guide walls 15 and 16 and defining a pulsating vacuum chamber or manifold 17. The pulsating vacuum chamber 17 is interconnected with the valve 12 through suitable tubing 18'. At the top of the chamber 17 are a series of slots 18 defined by scraping edges 19 of rectangular scraping elements 20 which extend transversely across the longitudinal axis of the cleaning head as best shown in FIGS. 1 and 2. The scraping elements define an interrupted planar surface indicated by dotted line 21 upon which a computer tape 22 is passed as in the direction of arrow 23 from a first computer tape reel 24 to a second computer tape reel 25 as will be described.

The exact number of slots 18 and parallel scraping edges 19 can vary considerably but in all cases at least two transversely extending slots and preferably two corresponding scraper edges are used. The rectangular slots 18 extend from side-toside of the cleaning head and extend past the side edges of the tape 22 leaving spaced gaps communicating with the vacuum chamber 17 on either side of the tape to allow passage of air during the cleaning operation as will be described. The gaps provide for a turbulent air flow and the total cross-sectional area of all the gaps is always less than the minimum crosssectional area of any passageway to the vacuum source or pump. Preferably the area for air leakage on the sides of the tape is predetermined to allow no more than 80 percent of the air flow present in the minimum cross-sectional area of any component between the vacuum source and the gaps. While the slots 18 are preferably rectangular in plan view as shown in FIG. 2, their configuration can vary. It is preferred that the slots have at least one straight scraping edge on the side of the head closest to the wind up reel 25 for best scraping action.

In the preferred embodiment, the scraping elements 20 are formed of a nonmagnetic tungsten carbide material having 90 angle upper corners forming scraping edges 19. However, the material and shape of the scraping elements can vary greatly. Magnetic materials can be used when the tape is a nonmagnetic tape. In some cases, the scraping elements can be knife edges rather than rectangular cross section elements as shown. Although the scraping edges are preferably located in a plane, they can lie on a radius or curve if desired.

In the embodiment 10, reel 24 is a standard computer tape reel mounted on a free-wheeling spindle which provides substantially no drag to the tape allowing free removal and unwinding of the tape while reel 25 is a driven reel which provides the required pulling force for taking up the tape on the reel 25. The free-wheeling reel 24 does have a slight amount of drag, for example, in the order of 2 ounces due to conventional bearing drag. Suitable idler rollers 27 and 28 can be provided if desired or eliminated as when the tape reels feed and take up the tape directly from the surface of the cleaning head defined by the plane 21.

The valve 12 is preferably an electric vacuum valve of the type described in U.S. Pat. No. 3,378,121 as for example a Model F-Vl electrovacuum valve produced by P. G. Foret, Inc. of Sudbury, Massachusetts. As shown schematically in cross section in FIG. 1, the valve provides a source of pulsating vacuum in the chamber 17 by interconnection ofa vacuum pipe 30 with the vacuum pump or source 13. An atmospheric outlet 32 is connected to a valve chamber 33 as is pipe 30 and tube 18'. A disc valve element 34 lies in the chamber 33. An electromagnetic coil or solenoid 35 is actuated by a pulsating electric power supply 14 in a known manner to switch the valve disc 34 from the position shown in FIG. 1, where it blocks vacuum to the chamber 17 permitting entrance of air, to a second position shown in dotted outline in FIG. 1 where air is cut off and vacuum applied to the chamber 17. The disc is made of a magnetic material as is known. Such valves are capable of operation at extremely high frequencies permitting vacuum pulsation at high rates which is important in the present invention. However, any valve capable of operation at the frequencies desired can be used. Similarly, the particular vacuum pump or vacuum source and pulsating power supply can vary as is known in the art to supply the required duty cycle of vacuum in the pulsating chamber 17. Preferably the vacuum source has a constant, unvarying vacuum in the range of from I to 28 inches of mercury.

Suitable drive mechanisms can be used to drive the reel 25 as is known in the art. It is possible to permit cleaning of the tape when passing in the direction of arrow 23 or reverse to that direction, by supplying suitable clutches to make reel 24 a driven roll and reel 25 a substantially free-wheeling roll. The tape speed can vary considerably but is preferably in the range of from 100 inches/second to 200 inches/second.

Preferably a vacuum filter is provided in line 30 to remove contaminates taken off the tape so that the device acts as a conventional vacuum cleaner. Conventional filters can be used such as found in home rug vacuum cleaners including disposable bags of paper or cloth.

In operation of the device 10, the vacuum pump is activated to provide a constant vacuum in pipe 30. Power supply 14 is activated to provide a predetermined duty cycle in valve 12 to create a pulsating vacuum in chamber 17. The tape 22 is then threaded on reel 25 which is then driven through a slip drive of any conventional type to allow constant drag and variable speed. The tape moves in the direction of arrow 23 with the portions of the tape over the cleaning head being pulled into the slots slightly to obtain thorough cleaning.

As best seen in FIG. 3, portions of the tape over each successive slot are pulled downwardly from the plane 21 to a lesser extent in each slot as the tape moves from left to right.

In a specific example, a standard 0.5 inch wide 2,400 foot long magnetic computer tape is cleaned. Chamber 17 has a volume of 0. 18 cubic inch. Five slots 18 are used each having dimensions of 0.125 inch length and a width (wall 15 to wall 16) of 0. 1 8 inch. The vacuum in pipe 30 is a constant vacuum of 10 inches of mercury. The duty cycle of valve 12 (Foret FVl) is 25 percent, i.e., the vacuum is applied fully 15 seconds per minute of operation to pulse the vacuum in chamber 17 60 times per second. The distance between each consecutive slot is 0.875 inch with each element 20 having a length of0.750 inch.

The tape 22 moves continuously over the surface of the cleaning head 1 l with its oxide coating contacting the scraper elements and with successive portions being drawn toward the chamber 17 as shown in FIG. 3. The tension or drag on the tape from the bearings of reel 24 is about 2 ounces while a constant winding tension in reel 25 is about 8 ounces. The tape speed is variable from 137 inches per second to 274 inches per second. The geometry of the slots and the dimensioning given cleans each portion of the tape as it passes from end to end of the cleaning head 11 at least in one slot. Thus the portion A of FIG. 3 is cleaned by being vibrated in the position shown in FIG. 3 in the first slot and may then pass over the next slots without being drawn into them but is preferably drawn into and cleaned again in the last slot on the right-hand side of the head 11 as shown in FIG. 3. By varying the tape speed, number and size of slots, distance between slots and duty cycle and frequency of the valve, the amount of cleaning in each continuous passage of the tape over the head 11 can be varied greatly as can the tension created by varied greatly to predetermined values. In the specific example the full tape is continuously moved and cleaned in about 2 minutes.

The information recorded on the computer tape is not in any way affected by the cleaning process.

The term frequency" as used herein indicates the time from the opening of the disc, to the full closed position shown in dotted lines in FIG. 1 and the return up to the time the disc again opens. The term duty cycle refers to the time it takes the disc 34 to move from the position shown in full lines to the position shown in dotted lines in FIG. 1 and return.

In the cleaning method of this invention, the scrapers formed by the degree angled edges 19, thoroughly clean both loose particles and bound, outwardly extending particles which extend above from the oxide surface of the tape. The passage of air about the side edges of the tape 22 provides a turbulent air flow, vacuuming action to carry away dust, dirt and oxide particles or other contaminates which are loose or loosened by the scraping edges and also provides for cooling of the scraping edges permitting excellent cleaning and insuring long life of the scraping edges.

The number and spacing of the slots in the cleaning head are designed so that any given point on the tape surface is subjected to at least one vacuum scraping cycle as it passes through the entire length of the cleaning head regardless of tape velocity. The degree of cleaning in the specific example at velocities of 137 inches per second to 274 inches per second is illustrated in FIGS. 4 and 5. The tape portions shown below the cleaning slots indicate which continuous portions of the tape are cleaned below each of the slots. It can easily be seen that overlapping portions of the tape as indicated in the drawing are cleaned as the tape passes over the head 11. As seen on the cross section of the tape 22 in FIGS. 4 and 5, the entire length of the tape passing over the head is cleaned with portions 51 being cleaned more than once and portions 52 being cleaned one time.

The device also provides a tension control since the vacuum pull on the tape to pull it down into the slots during passage over the cleaning head provides the required tension. The tension when passing the tape in either direction over the cleaning head can be determined by the following formula:

A =area of each vacuum slot N =the number of vacuum, slots V =available vacuum in inches of Hg K =duty cycle of pulsating vacuum K =constant load due to free-wheeling in the tape reel 24 F, =dynamic coefficient of friction between the oxide coating and the scraping edges In practice, the pulling tension is preferably adjusted so that it is in the range of from 7 to 9 ounces for use with computer tapes. Adjustment of the tension can be made simply by adjusting the duty cycle of the valve since the vacuum in the vacuum source is fixed.

it should be understood that although edges 19 are provided on either side of each slot for scraping, when the direction of the tape is toward the reel 25 asshown by arrow 23, only the scraping edges on the right-hand side of each slot are necessary to scrape the tape while when the direction of the tape is reversed, the left-hand side scraping edges 19 create a scraping action. Thus, if only one direction of travel of the tape will be used as in the direction of arrow 23, the left-hand edges 19 can be rounded and not act to scrape. In all cases the scraping edges do not cut into the oxide layer below the main surface thereof.

While a specific embodiment of this invention has been shown and described, it should be understood that many variations thereof are possible. For example, in all cases at least two slots 18 are used although the number of slots can be varied as can their dimensions. The slot width is preferably set for a given tape speed to control the maximum depth of penetration of the tape into the vacuum chamber as best seen in FIG. 3. Preferably all slots have access to a common chamber 17 connected to a high speed on-off vacuum valvewhich is in turn connected to a vacuum source although individual vacuum chambers underlying each slot can be used.

The tension on the tape can vary depending upon the type of tape being cleaned. The tension on the tape provided by the take up reel is proportional to the vacuum applied times the area of each slot times the number of slots and the frequency of the valve. At a fixed frequency and vacuum the tension will remain constant on the tape as it is passed through the device. The surface area of the tape exposed to the vacuum is determined by the overall area of the tape (width 1: length x number of slots) multiplied by the number of pounds per square inch of average vacuum (total vacuum x duty cycle) which is equal to the tension force applied to the tape.

In all cases, the area provided by the slots which expose the tape to the vacuum chamber is predetermined as is the distance between the slots to assure that each section of the tape which is continuously passed over the cleaning head is exposed to a vacuum and preferably to a scraping edge at at least one point. However, if only loose contaminates are to be removed from a surface of the tape, no scraping edges are used and edges 19 are rounded. In this case, the vibration of the tape passing over the cleaning head is effective to clean the tape. in some cases, only one or more of several slots are provided with scraping edges.

While the tape cleaning device is shown with reels 24 and 25 the cleaning head and associated vacuum pulsing components can be incorporated directly in an information recording or playback system such as by locating the device just before the recording head of a tape recorder.

Tapes of all types can be cleaned by the means and method of this invention. If no scraping action is desired with any tape as when the plastic surface of a computer tape is to be cleaned, the scraping edges can be roundedso that only the pulsating vacuum effect is used to clean loose particles from the surface as previously described. The term informationcarrying tape as used herein includes such tapes as audio tapes, video tapes, computer tapes, stripped tapes and the like both before and after information is stored on the tapes.

Successive cleaning heads such as 11 can be used on both sides of a tape intermediate winding reels to clean both surfaces of a tape in a single unwinding and winding step if desired. Alternatively, other cleaning means can be used to clean the plastic surface of the tape simultaneously with the cleaning action of head 1 1.

What is claimed is:

1. A method of cleaning a thin elongated, axially extending, information-carrying tape having side edges, said method comprising, 7

passing said tape in an elongated path over a plurality of slots positioned transverse to the path of said tape with said slots extending beyond said tape side edges,

at least two of said slots being defined in part by a scraping edge and having a vacuum chamber thereunder,

and applying a pulsating vacuum to said vacuum chamber to cause portions of said tape to be moved toward said vacuum chamber during continuous passage over said slots with said portions being cleaned by vacuum action and by a scraping of said scraping edge.

2. A method in accordance with the method of claim 1 wherein successive portions of said tape are drawn into said slots and vibrated during said passage to shake loose particles from the surface of said tape,

and a turbulent air flow is established about said side edges and in said vacuum chamber to remove said particles.

3. A method in accordance with the method of claim 2 wherein said scraping edges are parallel to each other and are aligned in a plane with said tape being passed over said plane.

4. A method in accordance with the method of claim 2 wherein said tape is unwound from a reel at substantially no tension and passed directly to said slots whereby said vacuum creates a tension in said tape and pull is applied to the leading edge of said tape as it is removed from said slots.

5. A method in accordance with the method of claim 2 wherein said tape is wound on a takeup reel after passage over said slots under a constant back tension provided by said pulsating vacuum.

6. A method of cleaning an elongated tape having side edges, said method comprising,

passing said tape in a path over a plurality of slots positioned transverse to said path with said slots extending beyond said side edges,

at least two of said slots being defined by opposing edges and having a vacuum chamber thereunder,

and intermittently applying a vacuum to said vacuum chamber during continuous passage of said tape thereover to cause portions of said tape to be drawn into said slots and vibrated during said passage with a turbulent air flow established about said side edges to remove unwanted particles from surface portions of said tape.

7. A method in accordance with the method of claim 6 and further comprising scraping said surface portions while subjecting said portions to said pulsating vacuum.

8. A method in accordance with the method of claim 6 wherein some portions of said tape are vibrated and cleaned while passing over one of said slots and said last-mentioned portions are not vibrated when passing over a second one of said slots.

9. A method in accordance with the method of claim 6 wherein said intermittent vacuum is applied to said vacuum chamber by alternately interconnecting said chamber with a vacuum source and a source of'etmospheric pressure through a high-frequency valve.

10. A method in accordance with the method of claim 9 wherein each portion of said tape is cleaned by vibrating when over at least one of said slots while only some portions of said tape are cleaned by said vibrating over at least two of said slots.

ll. A tape cleaning device comprising, means defining a plurality of seriatim arranged slots defined in part by seriatim arranged opposed edges,

means for passing an information-containing tape having side edges over said slots with one surface of said tape facing said edges and said slots extending beyond said tape side edges,

means defining a vacuum chamber underlying said slots,

and means interconnected with said vacuum chamber for applying a pulsating vacuum to said chamber as said tape is moved over said slots to urge portions of said tape into said slots and vibrate said portions as said tape is continuously moved past said slots whereby unwanted material is removed from said tape by said pulsating vacuum.

12. A tape cleaning device in accordance with claim 11 wherein five slots are defined by said slot edges,

and opposed edges of said slot comprise scraping means for aiding said cleaning action.

13. A tape cleaning device in accordance with claim 11 wherein said means for applying said pulsating vacuum pulses said vacuum at a predetermined rate coordinated with the rate of movement of said tape over said slots so that some portions of said tape passing over said slots are vibrated and cleaned at only one of said slots while other portions of said tape are vibrated and cleaned by at least two of said slots during a single passage of said tape over said slots.

14. A tape cleaning device in accordance with claim 13 wherein said means for applying a pulsating vacuum comprises a vacuum source and a high frequency valve for alternately connecting said chamber with said vacuum source and a source of atmospheric pressure.

15. A tape cleaning device in accordance with claim 14 wherein said slots are defined by parallel rectangular elements formed of a nonmagnetic material and defining thereunder an enclosed vacuum chamber.

16. A tape cleaning device in accordance with claim 14 wherein said edges are aligned substantially in a plane. 

2. A method in accordance with the method of claim 1 wherein successive portions of said tape are drawn into said slots and vibrated during said passage to shake loose particles from the surface of said tape, and a turbulent air flow is established about said side edges and in said vacuum chamber to remove said particles.
 3. A method in accordance with the method of claim 2 wherein said scraping edges are parallel to each other and are aligned in a plane with said tape being passed over said plane.
 4. A method in accordance with the method of claim 2 wherein said tape is unwound from a reel at substantially no tension and passed directly to said slots whereby said vacuum creates a tension in said tape and pull is applied to the leading edge of said tape as it is removed from said slots.
 5. A method in accordance with the method of claim 2 wherein said tape is wound on a takeup reel after passage over said slots under a constant back tension provided by said pulsating vacuum.
 6. A method of cleaning an elongated tape having side edges, said method comprising, passing said tape in a path over a plurality of slots positioned transverse to said path with said slots extending beyond said side edges, at least two of said slots being defined by opposing edges and having a vacuum chamber thereunder, and intermittently applying a vacuum to said vacuum chamber during continuous passage of said tape thereover to cause portions of said tape to be drawn into said slots and vibrated during said passage with a turbulent air flow established about said side edges to remove unwanted particles from surface portions of said tape.
 7. A method in accordance with the method of claim 6 and further comprising scraping said surface portions while subjecting said portions to said pulsating vacuum.
 8. A method in accordance with the method of claim 6 wherein some portions of said tape are vibrated and cleaned while passing over one of said slots and said last-mentioned portions are not vibrated when passing over a second one of said slots.
 9. A method in accordance with the method of claim 6 wherein said intermittent vacuum is applied to said vacuum chamber by alternately interconnecting said chamber with a vacuum source and a source of atmospheric pressure through a high-frequency valve.
 10. A method in accordance with the method of claim 9 wherein each portion of said tape is cleaned by vibrating when over at least one of said slots while only some portions of said tape are cleaned by said vibrating over at least two of said slots.
 11. A tape cleaning device comprising, means defining a plurality of seriatim arranged slots defined in part by seriatim arranged opposed edges, means for passing an information-containing tape having side edges over said slots with one surface of said tape facing said edges and said slots extending beyond said tape side edges, means defining a vacuum chamber underlying said slots, and means interconnected with said vacuum chamber for applying a pulsating vacuum to said chamber as said tape is moved over said slots to urge portions of said tape into said slots and vibrate said portions as said tape is continuously moved past said slots whereby unwanted material is removed from said tape by said pulsating vacuum.
 12. A tape cleaning device in accordance with claim 11 wherein five slots are defined by said slot edges, and opposed edges of said slot comprise scraping means for aiding said cleaning action.
 13. A tape cleaning device in accordance with claim 11 wherein said means for applying said pulsating vacuum pulses said vacuum at a predetermined rate coordinated with the rate of movement of said tape over said slots so that some portions of said tape passing over said slots are vibrated and cleaned at only one of said slots while other portions of said tape are vibrated and cleaned by at least two of said slots during a single passage of said tape over said slots.
 14. A tape cleaning device in accordance wiTh claim 13 wherein said means for applying a pulsating vacuum comprises a vacuum source and a high frequency valve for alternately connecting said chamber with said vacuum source and a source of atmospheric pressure.
 15. A tape cleaning device in accordance with claim 14 wherein said slots are defined by parallel rectangular elements formed of a nonmagnetic material and defining thereunder an enclosed vacuum chamber.
 16. A tape cleaning device in accordance with claim 14 wherein said edges are aligned substantially in a plane. 